“It turns out millions of people have PFAS in their drinking water,” Tracey Woodruff, director of the Program on Reproductive Health and the Environment at the University of California, San Francisco, tells Fortune. 

The Environmental Working Group (EWG) found that roughly 60% of the U.S. population—about 200 million people—are served by water systems that have the chemicals PFOA or PFOS in their drinking water at a concentration of 1 part per trillion or higher, which is the maximum limit for PFAS in drinking water endorsed by the EWG.

“It’s widespread,” Woodruff says.

Also known as “forever chemicals,” PFAS—short for per- and polyfluoroalkyl substances—are chemicals widely used in manufacturing that are toxic to humans and animals and break down slowly over time, hence their “forever” nickname. They are also known to be endocrine disruptors, chemicals that interfere with our endocrine systems, which control the body’s hormones—such as insulin, testosterone, and estrogen—and numerous bodily functions, including metabolism and blood sugar regulation.

Knowing there are chemicals in your water is one thing—but should you be worried? And is there anything you can do to reduce your exposure? Here’s everything you need to know, according to experts who spoke with Fortune.

How do PFAS chemicals get in drinking water?

There are several ways that PFAS chemicals can enter drinking water, according to environmental and public health scientist Mindi Messmer. 

Potential sources include: 

• Industrial sites that use PFAS in their manufacturing can pollute nearby water sources through the soil or air
• Landfills—particularly unlined ones—that can leach PFAS chemicals into groundwater
• Biological waste used as fertilizer on soil that may contain PFAS
• Military bases with fire training areas that use PFAS-containing aqueous film-forming foam to extinguish flames

“It’s a sampling of things,” Messmer tells Fortune.

“If it’s deposited onto the ground, because it breaks down over a very long period of time, the PFAS contamination could last, from our perspective, forever, and it could also accumulate,” Woodruff tells Fortune. “That’s why it’s really important that these types of chemicals not be put out into the environment, or not even made in the first place.”

Most municipalities are required to submit PFAS testing data to the Environmental Protection Agency, Messmer says. To find out if there have been PFAS chemicals detected in your water supply, you can check the EWG database, or contact your local water system to find out.

Are PFAS harmful?

According to the Environmental Protection Agency, PFAS chemicals are linked to the following potential health effects:

• Decreased fertility or increased high blood pressure in pregnant women.
• Developmental effects or delays in children, including low birth weight, accelerated puberty, bone variations, or behavioral changes.
• Increased risk of some cancers, including prostate, kidney, and testicular cancers.
• Suppressed immune system, inhibiting the body’s ability to fight infections and reduced vaccine response.
• Hormone disruption.
• Increased cholesterol levels and/or risk of obesity.

Woodruff is particularly concerned about low birth weight in newborns, which impacts one of the most vulnerable populations. 

“Even though PFAS itself doesn’t cause infant mortality, it does increase the risk of a condition that can increase the risk of an infant dying,” she says. 

Other potential health effects are still being studied, Woodruff adds, including links to breast cancer and gestational diabetes. 

If you are concerned—or know—that you’ve been exposed to PFAS chemicals, the National Academy of Sciences has developed clinical guidelines to potentially test your blood for PFAS levels and instruct how to take steps forward with your provider.

“At least now we know more than we used to know,” Messmer says.

Are PFAS chemicals in drinking water regulated?

Last year, the Biden administration passed the first-ever national drinking water standard for PFAS chemicals. 

That administration’s EPA announced limits for five individual PFAS: PFOA, PFOS, PFNA, PFHxS, and HFPO-DA (also known as “GenX Chemicals”). Each type of PFAS chemical varies in chain length, structure, and how they interact in the human body. The rule also sets a limit for mixtures of any two or more of four PFAS: PFNA, PFHxS, PFBS, and GenX chemicals. However, Woodruff points out, there are 15,000 potential PFAS chemicals out there, so there could be other unregulated ones still in some people’s water.

For PFOA and PFOS in particular, the EPA set the Maximum Contaminant Levels at 4.0 parts per trillion, but stated they have a “non-enforceable health-based goal” of zero, based on research that reflects “there is no level of exposure to these contaminants without risk of health impacts, including certain cancers.” The standard for the rest of the chemicals is set at 10 parts per trillion.

Recently, the Trump administration announced they would uphold the limits for just two of the five PFAS chemicals, but would be delaying the enforcement. They also stated they would be reevaluating regulation for the other four chemicals.

“It’s really important that the government does its job,” Woodruff says.“This is why these cuts to the EPA are so, so bad.”

Can you remove PFAS from your tap water?

Unfortunately, there isn’t much that you can do to rid PFAS from your tap water, Woodruff and Messmer say. Messmer knows that there is PFAS in her tap water—and chose to invest $7,000 in a home filtration system for her entire house.

There is potential for regular water filters to reduce your PFAS exposure: The EWG evaluated the effectiveness of home water filters and found four that could get the job done. 

Messmer and Woodruff also encourage contacting your local water district to find out PFAS levels in your water supply, and urge them to clean it up when possible. If you use a private well or are on a much smaller water system, Messmer encourages trying to test the water for PFAS yourself.

Some people may opt to switch to bottled water. Earlier this year, the FDA tested 197 bottled water samples for 18 types of PFAS, including the six chemicals currently regulated under the Safe Drinking Water Act. While 10 samples tested positive for PFAS, none of those exceeded the maximum contaminant levels (MCLs) set by the EPA for drinking water. However, it’s important to keep in mind that drinking bottled water could increase your exposure to microplastics, which come with their own variety of potential negative health impacts on brain health, fertility, and the gut microbiome (not to mention the environment). 

But ultimately, government regulation is the best solution, experts say. 

“There’s only a certain amount of control you have over it,” Messmer says. “We deserve for our government to take steps to protect us.”

For more on chemicals:

• Eating more fiber could help reduce the amount of forever chemicals in your blood, study finds
• The truth about American drinking water: Report shows widespread presence of hazardous chemicals
• More than 113 million people are drinking tap water that contains a newly identified chemical—and nobody knows if it’s toxic or not
• Beer is the latest source of hazardous PFAS, or ‘forever chemicals,’ according to worried scientists